Radio signaling system



Nov. 30 1926.

C. S. DEMAREST ET AL RADIO SIGNALING SYSTEM Filed Deo. zo. 1925 NNN ATTORNE Y Patented Nov. 30, 1926.

UNITED STATES PATENT OFFICE.

CHARLES S. DEMAR-EST, OF RIDGEWOOD, AND RALPH K. BONELL, 0F EAST ORANGE,

NEW JERSEY, ASSIGNORS TO AMERICAN TELEPHONE AND A CORPRATON OF NEW YORK.

TELEGRAPH COMPANY,

RADIO SIGNALING SYSTEM.

Application filed December 30, 1925.

This invention relates to signaling systems, and more particularly toarrangements in such systems for selectively transmitting and receivingsignals between a primary or central station and a plurality ofsecondary stations constituting a high-frequency communication system,which system employs a single signaling frequency or a relatively narrowband of signaling frequencies.

lIn a high-frequency communication system comprising a primary orcentral station and a plurality of secondary or distant stations, it isdesirable that the primary station should be able to call any one of thesecondary stations without at the same time signaling any ot the othersecondary stations. It is also desirable to have arrangements that willenable any one ot the secondary stations to call the primary stationwithout at the same time signaling any of the other seconda-ry stations.It is further desirable to have arrangements at the primary station torindicating which one of the secondary stations is calling the primarystation.

lt is an object of this invention to provide a selective signalingsystem whereby any secondary station may be called by the primarystation to the exclusion ot all other secondary stations.

lt is another object ot' this invention to provide a selective signalingsystem whereby any one ot the secondary stations may call the primarystation.

It is a further object of this invention to provide means at the primarystation for indicating which one of the secondary stations is calling aprimary station.

lVhile the nature ot the invention will be pointed out withparticularity in the appended claims the invention itself, both as toits objects and features, will be better understood from the detaileddescription hereinafter ollowin g when read in connection with theaccompanying drawing which represents one form of embodiment of theinvention. lt will be understood that although the invention will beshown and described in one particular embodiment, it may be shown anddescribed in various other embodiments within the scope of the appendedclaims.

Referring to the drawing, a primary station is schematically shown whichincludes wiring and equipment to be used at the pri- Serial No. 78,452.

mary station for transmitting and receiving calling signals and voicesignals between the primary station and a plurality of secondarystations (not shown). These secondary stations and the primary station,when taken together, might represent a ship-to-shore system of wirelesstelephone communication in which the drawing represents the shorestation and the secondary stations (not shown) represent the shipstations.

The rectangle ST represents a subscribers telephone or telegraph set orthe switchboard terminal equipment in a local telephone control orhce.This subscribers telephone set is connected through a line SL by meansof a plug P to a main line or circuit ML for the transmission ofsignals. Speech transmitting and receiving circuits TL and RL areassociated with the main line ML through a balanced transformer orhybrid coil HC. In order that the circuits TL and RL may be renderedconjugate with respect to the main line ML so that the electricaldisturbances in one ot these circuits will be without e'lect upon theother, the main line ML is balanced. by a balancing network N.

A radio transmitter RT is connected to the speech transmit-ting circuitTL through the cont-acts l and 2 of a transmitting relay TR when speechsignals are being transmitted. A radio receiver RR is connected to thecommon receiving circuit RL through the contacts l and 2 of a relay R,when speech signals are being received. The radio transmitter RTcomprises means for modulating a carrier current by speech or voicesignals or by low frequency calling signals for transmission by a commontransmitting antenna TA to any one of the secondary stations. The radioreceiver ER comprises means for demodulating the speech or voice signalsor low frequency calling signals from the modulated carrier currentreceived by the common receiving antenna RA as transmitted by any one ofthe secondary stations.

For the reception of low frequency calling signals the winding of therelay R, becomes de-energized, as will be explained hereinafter, toconnect the output ot the radio receiver RR with a signal receivingcircuit SR. For the reception of voice curn rent the relay B, becomesenergized for connecting the output of the radio receiver RR with thespeech receiving circuit RL'. For the transmission ot low frequencycalling signals the Winding of the transmitting relay TR becomesenergized, as will be eX- plained hereinafter, for connecting the lovvfrequency signaling source G1 oi, for eX- ample, 135 cycles, with theradio transmitter1 RT through the calling signal transmitting circuitCT. For the transmission ot voice signals the transmitting relay TRbecomes cle-energized so that the speech transmitting circuit TL isconnected Wit-h the radio transmitter BT.

There are shown a plurality of jacks, J1 to J1, inclusive, eachcorresponding to one ot the secondary stations to Which the transmissionand reception of signals may be established. Associated With these jacksJ1 to J1, inclusive, are line lamps, L1 to L1, inclusive, each ot whichlights when incoming calling signals are received, :thus indicatingwhich one of the secondary stations is calling the primary station.`While only tour channels of transmission have been indicated in thedrawing, it Will be understood that any number o t transmission channelsmay be included Without impairthe effectiveness of the invention.

For the transmissionV of calling signals, coded Aimpulses characteristicof each of the secondary stations are produced by the opening and`closing of contacts brought about by cams CS1 to CS1, inclusive, whichare all mounted on the same rotatable cam shaft CS, which is driven bythe motor M in the direction indicated by the arrow.

lFor the reception ot callingsignals, coded impulses characteristic ofeach of the secondary stations are selected by selectors S1 to S1,inclusive, into an appropriate channel. The operation of the selectorsWill be referred to only generally herein since a more detaileddescription of the selectors may be found in the patent to J. C.Fielch'llo. 1,343,256, dated .lune 15, 1920. For the sake of simplicitythe selectors are shown schematically.

The operation or' the system tor the transmission ot a calling signalfrom the primary station to one ot the secondary staions will now bedescribed. The plug .P is inserted in a jack, for example, J1 which isassociated with a channel corresponding to one of the secondarystations. The ringkey K is then operated, thus connecting a ringinggenerator G1 with the main line ML. This ringing generator may be, forexample, generator capable ot' transmitting Current ot 20 cycles. nnalternating current relay Tl, is bridged across the main line ML inseries with a condenser and the armature of this relay is attracted whenthe hey l is operated. This then causes the deenergization of thewinding of a direct current relay R3, hus putting ground on a conductor11 by virtue of the release of the armature of the relay Also, when theplug P engages the jack J1 the Winding oit the relay lv t1 becomesenergized by the iiow of current from the battery B1 through the sleeveof the jack J1 and the Winding ot the relay MB1. Then the armatures otthe relay li/EB1 are attracted, closing contacts 1 and 2 and openingcontactll ol that relay. By closing contact 2, current from the batteryflows through the Winding ot a transmitting selectingl relay TS1 in acircuit which includes battery B1, cont-act 2 of relay MR1, conductor12, the Winding of the transmitting selecting relay TS1, conductor 11and the armature oi' the relay R11. The transmitting selecting relay TS1then brings about the operation o'l` a motor relay MB, starts inrotation the motor and the rotatable cam shaft CS associated with it.This then prepares the circuits for the transmission of a `coded impulsecharacteristic oi" one of the secondary stations, as will be explainedhereinafter.

The transmitting selecting relay TS1, when energized, closes threecontacts, 1, 2 and 3. Contact 1 puts a locking ground on the Winding ofthis relay through the contact established by the armature controlled bythe release cam RC. Contact 2, controlled by the transmitting selectingrelay TS1, closes the circuit including the Winding or' the motor relayMR. This circuit includes battery B3, the winding of the motor relay MR,conductor 14, contact 2 ot' the transmitting selecting relay TS1 andconductor 13. As Winding ot the relay MR becomes energized its armaturesare attracted, closing contacts 1 and 2'associated therewith. Contact 1of the motor relay MR causes the operation of the motor M by a flow or'current through the field and armature of the motor from a battery B1.Contact 2 of the relay MR closes a circuit which brings about theenergization of the Winding of a cut-off relay R4. This circuit includesa battery mwvinding ot' the cut-oli relay R1, conductor 17, and contact2 oi the motor relay MR. The operationoie the cut-oil relay 'R1disconnects the main line ML from the line SL connected to thesubscribers telephone set ST. Contact 3 ot the transmitting selectingrelay TS1 closes the circuit including the Winding ot the transmittingrelay TR as the rotatable cam shat CS revolves. This circuit includes abattery B6, the Winding of the transmitting relay TR, conductor 15,contact 3 ot' the transmitting selecting relay TS1 and the armature andcontact associated with the camv CS1. lfshenever the Winding of thetransmitting relayy TR becomes energized, loW frequency signalingcurrent of, for

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example, 135 cycles, from the source G1 is transmitted to the radiotransmitter RTl through the calling transmitting circuit CT. The caniCS, is mounted on the rotatable cam shaft CS and is so formed as totransmit a signal characteristic of one of the secondary stations fromthe primary station to that secondary station. The calling` signaltherefor consists of spurts of low frequency signaling current of 135cycles, which is superimposed at the radio transinitter RT on a carriercurrent of suitable high frequency.

After the signal characteristic of the secondary station has beencompletely transmitted the release cam RG momentarily takes ground offthe contact l of the transmitting selecting relay TS1 and brings about ade-energlzation of this relay. As the transmitting selecting relay TS1releases, it opens the circuit to the motor relay MR which includes theconductor 13, contact 2 of the transmitting selecting relay TS1,conductor 14 and the Winding of the motor relay MR. All of the cams CS1to CSM inclusive, are mounted on the same rotatable cam shaft CS; andeach is so formed as to transmit a signal characteristic of one of thesecondary stations.

All of the secondary stations of the system receive the modulated highfrequency current, and each of these secondary stations has selectingmeans thereat Which is responsive to a calling signal characteristic ofthat secondary station. The selecting means employed at the secondarystations may be selectors of the type disclosed in the patent to J. C.Field, mentioned hereinabove.

The reception of a calling signal characteristic of one of the secondarystations is received at the primary station in a inanner which Will nowbe described. At the secondary station there may be a rotatable camshaft having a cam thereon so formed as to transmit a signalcharacteristic of that secondary station. That calling signal istransmitted on a carrier current in a manner similar to the transmissionof calling signals at the primary stations by means of radio transmitterRT. This calling signal is received by the radio receiver RR through thecommon receiving antenna RA. 1When voice signals are not being receivedthe relay R1 remains cle-energized and the calling signal, after beingdemodulated from the carrier current at the radio receiver RR, istransmitted to the signal receiving circuit SR. The Output of the signalreceiving circuit SR is connected to the calling signal receivingchannel CR in the output of which there areV a plurality of selectors,one corresponding to each of the secondary stations,` each beingresponsive to a calling signal characteristic of one of the secondarystations. lWhen a calling signal is received Which corresponds to thesignal to Which the selector Sl is responsive, the relay Lft-l, will beoperated by the connection of ground at the selector S1. As the Windingof the relay LR1 is energized its armatures are attracted, closingcontacts 1 and 2 of the relay. The closure of contact 1 lights the lampL1, thus indicating at the primary station which one of the secondarystations is transmitting a calling signal. It will be understood thatWhile a lamp has been employed for indicating which secondary station istransmitting a calling signal, that any other indicating means, Whethervisual, audible, or otherwise, may be employed instead thereof.

Contact 2 of the relay Lift1 locks relay LRI through Contact 3 of relayMB1. Thus the lamp Ll remains lit until the plug P engages the jack J1.When the plug l? engages the jack J1 the relay MB1 becomes energized bythe flow of current through the Winding thereof from battery B1. Thisbrings about the opening` of contact 3 of the relay MRI and unlocks theWinding of the relay LRl. As the winding of the relay Lit, becomesrie-energized the light of the lamp L, becomes extinguished. As contact1 of the relay MB1 becomes closed, current flows from the battery BTthrough Contact 1 of the relay Mll, conductor 19, and the winding of therelay R1. As the Winding of relayl R1 becomes energized its armaturesare attracted, closing contacts 1 and 2 thereof and cci'inecting theoutput of the radio receiver RR with the speech receiving circuit RL.This then puts the main line Mlrzin condition for the reception of voicecurrents.

Although the transmission and reception of calling signals at theprimary station has been described for only one channel corresponding toone secondary station, it will be understood that the transmission andreception of calling signals at the primary station for the otherchannels corresponding to the other secondary stations takes place in asimilar manner, and the description of the one channel will be deemedsuicient to describe the other channels.

lVhile the callingl signals have been described herein as produced byapparatus which includes rotatable cani shafts having cams thereon soformed as to set up characteristic signals, it Will be understood thatother apparatus well known in the art may equally Well be eniployed forproducing these calling signals.

llVhile the arrangements of this invention have been disclosed in oneembodiment, it is to be understood that the invention may bc embodied inother and Widely varied oricc ganizations Without departing from thespirit of the invention and the scope ot the appended claims.

i/Vhat is claimed is:

1. In a radio signaling system, a central station, a plurality ofsecondary stations, a plurality ot radio transmission circuitsinter-connecting said central station and said secondary stations, oneradio transmission circuit for each secondary station, a rotatable vcamshaft at each secondary station having a cam thereon so toi-med as totransmit a signal characteristic ot the corresponding radio transmissioncircuit, a plurality or' selectors at said central station, onecorresponding to each secondary station, each selector responding to asignal characteristic oil the corresponding radio transmission circuit,and means at the central station i'or indicating which secondary stationis signaling the central station.

2. In a radioV signaling system, a central station, a plurality otdistant stations, a plurality ot transmission circuits interconnectingsaid distant stations and said central station, one transmission circuitassociated with each distant station, a rotatable cam shaft at eachdistant station having a cam thereon so formed as to transmit a signalcharacteristic oit the corresponding transmission circuit, a rotatablecam shai't at the central station having a plurality oi cams thereon,each cam at the central station so formed as to transmit a signalcharacteristic ot the corresponding transmission circuit, a plurality ofselectors one at each distant station responsive to a sig4 nalcharacteristic of the corresponding transmission circuit, a pluralityoi' selectors at the central station, each responsive to a signalcharacteristic ot a corresponding transmission circuit, and means at thecentral station for indicating which distant station is transmitting asignal to the central Station.

3. VIn a radio signaling system, a plurality ot radio transmissioncircuits, a rotatable cam shaft having a plurality of cams thereon onecorresponding to each radio transmission circuit, each cam vbeing soformed as to transmit a signal characteristic of the corresponding radiotransmission circuit, means responsive to an outgoing signal Ato causethe corresponding cam to transmit the signal characteristic of thatradio transmission circuit to a distant station, means at the distantstation responsive to the characteristic signal thus transmitted, andmeans at the distant station for indicating the radio transmissioncircuit over Which a signal is being transmitted.

et. In a radio signaling system, a central station, a plurality ofdistant stations, a plurality of transmission circuits interconnectingsaid central station and said distant stations, one transmission circuitcorresponding to each distant station, a rotatable cam shatt'at thecentral station having Va plurality of cams thereon one associated witheach transmission circuit, each cam being so `formed as to transmit asignal characteristic of the corresponding transmission circuit, meansat the central station responsive to an outgoing signal to cause thecorresponding ca'm to transmit the signal characteristic of that circuitto a distant station, means at the distant station responsive to thecharacteristic signal thus transmitted, means 4at each distant station'for transmitting the signal characteristic ot the correspondingtransmission circuit to the central station, and means at the centralstation :tor indicating which one otthe distant stations is transmittinga signal. i i

5,. Ina radio signaling system, af central station, a plurality of"distant stations, a plurality ot transmission circuits interconnectingsaid distant Vstations and said central station, one transmission'circuit tor each distant station, la rotatable cam shaft at each distantstation having a cam thereon so formed as to transmit a'signalycharacteristic ot' that distanti'station, a rotatable cam shaft at lthecentral station having a plurality of cams' thereon Yeach so t'or'med asto transmit a signal character istic ot a distant station, apluralityotiselectors, one at each distant station responsive to asignal characteristic ot' thatdistant station, a plurality otselectorsmat the central station each responsive toa signalcharacteristic ot' a distant station, 4and means at the central stationtor indicating which distant station is transmitting a nalH tothecentra'l station.

v6. ln a radio signaling system, a plurality of'secondary stations eachhaving aradio transmitter anda radio receiv'ei,`fa`central station alsohaving a radio transmitter vand a radio receiver, means'at eachsecondary station for setting up and transmitting a coded signalycharacteristic of that secondary station to the central station," meansat the central station tor'setting up and transmitting a plurality otcoded signals eaeli characteristic of a secondary station, means at thesecondary station for responding to a coded signal characteristic otthat secondary station transmitted by the central station, means at thecentral station tor yresponding to a `coded signal characteristic ot asecondary station transmitted by the secondary station, and means torindicating which secondary station is transmitting a coded signal to thecentral station. i i

7. ln a radio signaling system, a primary station, a plurality of`secondary stations, circuit arrangements at said stations suitable orthe transmission and reception of speech signals by radio, means at eachseclli) ondary station for setting up a coded signal characteristic oi asecondary station it'or transmission to the primary station, means atthe primary station for setting up a plurality of coded signals eachcharacteristic of a secondary station, for transmism sion to thesecondary stations, means at the primary station for responding toreceived coded signals characteristic of the secondary stations, andmeans for indicating Which secondary station is transmitting a codedsignal to the primary station.

8. In a radio signaling system, a primary station, a plurality ofsecondary stations, all of the stations being adapted to transmit acarrier current modulated in accordance with calling signals of lowfrequency current, means at each secondary station for generating acalling signal characteristic of that station, means at the primarystation for generating a plurality of calling signals eachcharacteristic of a secondary station, a generator at cach station forgenerating a carrier current upon which the calling signal is modulated,a demodulator at each station for separating the calling signal from thecarrier current, a selector at each secondary station selectivelyoperated bv the calling signal characteristic of that station to theexclusion of all other signals, a plurality of selectors at the primarystation, one corresponding to each secondary station each selectivelyoperated by the calling signal characteristic of a secondary station tothe exclusion of all other signals, and means to indicate whichsecondary station is calling that primary station.

In testimony whereof, We have signed our names to this specificationthis 28th day of December, 1925.

CHARLES S. DEMAREST. RALPH K. BONELL.

